The term 4G wireless literally refers to fourth-generation wireless technology, but apparently there's not much else that buyers can count on when it comes to the 4G label .

T-Mobile USA this month reignited the debate over the definition of a 4G network when it launched TV ads claiming that it operates "America's largest 4G network."

Competitors said that T-Mobile's High-Speed Packet Access (HSPA+) network shouldn't be described as either "next generation" or 4G at all. In fact, T-Mobile last summer was calling basically the same HSPA+ network "the fastest 3G network."

"I'm afraid that carriers desperate for one-upmanship will make 4G a meaningless technical term," said Gartner Inc. analyst Ken Dulaney. "All it's going to mean is that it's faster than the last network you were on."

T-Mobile defended its use of the term 4G. "What we're selling today is clearly the equivalent or the better of what's being marketed today as 4G," said Mark McDiarmid, senior director of engineering at T-Mobile. The HSPA+ network delivers, on average, 5Mbit/sec. downstream to smartphones and 12Mbit/sec. to laptop dongles, he said.

Until recently, 4G referred to cellular networks using either WiMax or Long Term Evolution (LTE) technologies.

But the International Telecommunication Union ruled on Oct. 21 that WiMax and LTE in their current forms don't qualify as 4G. The ITU reserves that moniker for networks that achieve speeds of 100Mbit/sec., or about 10 times the performance that any carrier, including T-Mobile, can offer today.

The ITU said that the only technologies that will qualify as 4G are a future version of LTE to be called LTE-Advanced, and the next generation of WiMax, officially known as IEEE 802.16m or WirelessMAN-Advanced. Neither is expected to go live commercially until 2014 or 2015.